Mixing approach for 3D printable concrete: method of optimisation of superplasticiser dosage

This study is a systematic investigation of superplasticiser (SP) addition methods and optimum SP dosage with various water-to-binder ratios (w/b) for mixing three-dimensional printable concrete. In this study, five distinct strategies were adopted to arrive at the optimum method of addition. In the first strategy, a random mixing approach was applied to identify, through visual observation, methods for adding SP with varying time patterns. Secondly, a constant time pattern was adopted from the random approach for mixing and the optimal SP dosage was determined. In the third strategy, different methods of adding the optimum SP dosage were examined. In the fourth strategy, the batching effect of the material with the optimum SP dosage was assessed. Finally, the printable regions with different values of w/b and SP dosages were correlated. It was observed that the optimum SP dosage, in the range of 0.10–0.21% of binder, with w/b = 0.21–0.25 achieved adequate printability parameters by full addition of SP following a constant wet mixing time as the optimal application. However, after applying the optimum SP dosage, a supplemental SP dosage is required at appropriate intervals to retain the workability for higher batches.